We could supply all our energy needs without altering the global climate.

Is there not enough wind blowing across the planet to satiate our demands for electricity? If there is, would harnessing that much of it begin to actually affect the climate?

Two studies published this week tried to answer these questions. Long story short: we could supply all our power needs for the foreseeable future from wind, all without affecting the climate in a significant way.

The first study, published in this week’s Nature Climate Change, was performed by Kate Marvel of Lawrence Livermore National Laboratory with Ben Kravitz and Ken Caldeira of the Carnegie Institution for Science. Their goal was to determine a maximum geophysical limit to wind power—in other words, if we extracted all the kinetic energy from wind all over the world, how much power could we generate?

In order to calculate this power limit, the team used the Community Atmosphere Model (CAM), developed by National Center for Atmospheric Research. Turbines were represented as drag forces removing momentum from the atmosphere, and the wind power was calculated as the rate of kinetic energy transferred from the wind to these momentum sinks. By increasing the drag forces, a power limit was reached where no more energy could be extracted from the wind.

The authors found that at least 400 terawatts could be extracted by ground-based turbines—represented by drag forces on the ground—and 1,800 terawatts by high-altitude turbines—represented by drag forces throughout the atmosphere. For some perspective, the current global power demand is around 18 terawatts.

The second study, published in the Proceedings of the National Academy of Sciences by Mark Jacobsen at Stanford and Cristina Archer at the University of Delaware, asked some more practical questions about the limits of wind power. For example, rather than some theoretical physical limit, what is the maximum amount of power that could actually be extracted by real turbines?

For one thing, turbines can’t extract all the kinetic energy from wind—no matter the design, 59.3 percent, the Betz limit, is the absolute maximum. Less-than-perfect efficiencies based on the specific turbine design reduce the extracted power further.

Another important consideration is that, for a given area, you can only add so many turbines before hitting a limit on power extraction—the area is "saturated," and any power increase you get by adding any turbines ends up matched by a drop in power from existing ones. This happens because the wakes from turbines near each other interact and reduce the ambient wind speed. Jacobsen and Archer expanded this concept to a global level, calculating the saturation wind power potential for both the entire globe and all land except Antarctica.

Like the first study, this one considered both surface turbines and high-altitude turbines located in the jet stream. Unlike the model used in the first study, though, these were placed at specific altitudes: 100 meters, the hub height of most modern turbines, and 10 kilometers. The authors argue improper placement will lead to incorrect reductions in wind speed.

Jacobsen and Archer found that, with turbines placed all over the planet, including the oceans, wind power saturates at about 250 terawatts, corresponding to nearly three thousand terawatts of installed capacity. If turbines are just placed on land and shallow offshore locations, the saturation point is 80 terawatts for 1,500 terawatts of installed power.

For turbines at the jet-stream height, they calculated a maximum power of nearly 400 terawatts—about 150 percent of that at 100 meters.

These results show that, even at the saturation point, we could extract enough wind power to supply global demands many times over. Unfortunately, the numbers of turbines required aren’t plausible—300 million five-megawatt turbines in the smallest case (land plus shallow offshore).

What about the impacts of too many wind turbines on the climate? Both studies addressed this issue. The first study found that, as you might expect, if we extract wind power at the geophysical limit—removing all of the available kinetic energy from the wind—there are significant impacts on the climate. With only ground turbines, the average global temperature would increase by a few degrees Celsius, while high-altitude turbines would lead to a global cooling of more than ten degrees.

At the much more reasonable power levels of simply meeting global demands, both studies reported minimal environmental impacts. Local temperatures could change around 0.1 degrees Celsius, while local precipitation could be affected by about 1 percent.

Of course, knowing that there is enough wind energy to supply all our needs doesn’t necessarily mean we are going to harness it. Economic and political hurdles will have to be overcome, but knowing that the environmental impact would be minimal should reassure some critics.

Promoted Comments

Didn't realise there were any climate implications of wind turbines; that's interesting.

Could someone please enlighten me though as to why there's two quoted numbers, like the 250 terwatts vs 3000 terwatts? Tad confused..

" Jacobsen and Archer found that, with turbines placed all over the planet, including the oceans, wind power saturates at about 250 terawatts, corresponding to nearly three thousand terawatts of installed capacity. If turbines are just placed on land and shallow offshore locations, the saturation point is 80 terawatts for 1,500 installed terawatts of installed power. "

Wind turbines are rated in terms of the amount of power they could produce if the wind was blowing at the maximum speed they're able to handle; that's the 1500/3000TW number. But since the wind rarely blows at that level and power extracted is a function of windspeed cubed the average power produced is much lower, that's the 80/250TW number.

the saturation point is 80 terawatts for 1,500 installed terawatts of installed power.

Kyle can you delete one of these "installed"s?

Also, you should explain that those 10km-high wind turbines are a flying kite style wind turbine that is on the drawing board.

Obviously some people in the forum don't understand the value of this study. First, in the past some (crazy) people worried that all the wind turbines we are installing could cause climate change. They do cause local wind speed reduction (duh) and some local temperature increase. So does this imply a global climate effect? So these new studies ask a few questions: What's the most energy we could possibly get out of the global winds with maximum possible installation of wind turbines. They DID NOT imply that we should/could/will do this. They calculated how much power we could possibly get out of the global winds, and then determined that there WOULD be a significant climate effect IF we extracted the MAXIMUM POSSIBLE power from the wind. They also noted that the MAXIMUM POSSIBLE power we could get out of the wind is MANY TIMES MORE than today's total global electrical demand.

Then they moved to the next scenario. What if ALL of the world's CURRENT ELECTRIC DEMAND were supplied by wind turbines? They found that that amount of power extraction from the wind WOULD NOT cause a significant global climate effect.

172 Reader Comments

I recently asked a question similar to this one of Randal Monroe for his What-if series. Hoping he gives an entertaining answer soon. The Register has a different take on this particular story and looks at the assumptions the report made of electricity demand and then thinks about the costs involved in installing all these turbines.

I generally try to not to ding articles as I'm sure that in almost all cases they are genuinely trying to convey information in a best faith manner. That said though, in my opinion there is a serious disconnect between 'in theory' and 'in actuality' in this article.

I generally try to not to ding articles as I'm sure that in almost all cases they are genuinely trying to convey information in a best faith manner. That said though, in my opinion there is a serious disconnect between 'in theory' and 'in actuality' in this article.

LOL @ turbines at 10km altitude. Just how do they propose getting all that power back down to the ground? They gonna build towers that tall? I'd like to see that. I'm sure the FAA would love it, too. You could go the dirigible route like some are doing now on a small scale, but those are MUCH smaller and only go up a couple hundred feet or so. Good luck dangling 10,000 meters of 350MCM (or larger) DLO cables (anywhere between 8-20 of them) to support each 1MW turbine. You'd need a goddamn Zeppelin to support all that weight, oh, and by the way, they'd have to be the biggest Zeppelins ever built by far. It would only be feasible if you loaded the thing up with batteries that you'd send up to altitude, run for a while to charge, retrieve the unit when fully charged, swap the batteries out with a fresh set, send the balloon back up while plugging your charged-up batteries into the grid.

Or how about we install 4000 Gigawatt nuclear plants instead. Use far less real estate, you can put them anywhere they're needed, and if built properly (IE containment domes and modern safety systems) won't hurt anyone.

Just because wind power is fashionable doesn't make it good engineering!

I generally try to not to ding articles as I'm sure that in almost all cases they are genuinely trying to convey information in a best faith manner. That said though, in my opinion there is a serious disconnect between 'in theory' and 'in actuality' in this article.

Uh, yeah. The article actually calls that out.

I understand that. I also read where the article goes on to say that the lower limit of 300 million turbines is not practical or even really feasible. A quick bit of math would roughly indicate one turbine per square mile of the earths surface with the surface of the earth calculated at ~316,900,000 mi sq. This does not include turbines located 10km up in the jet stream where current engineering restraints meet airplanes somehow. My point is, and Psygard noted as well, this article ultimately comes off in the end as speculation and conjecture at best.

Storage, storage, storage. The problem with wind isn't that there isn't enough of it, it's that it doesn't blow in the right place at the right time. Here in the southern US we need electricity to run air conditioning on hot summer afternoons when the air is stagnant. How do you get the power from where the wind is blowing to where it's not blowing? Or store it until it's needed?

Didn't realise there were any climate implications of wind turbines; that's interesting.

Could someone please enlighten me though as to why there's two quoted numbers, like the 250 terwatts vs 3000 terwatts? Tad confused..

" Jacobsen and Archer found that, with turbines placed all over the planet, including the oceans, wind power saturates at about 250 terawatts, corresponding to nearly three thousand terawatts of installed capacity. If turbines are just placed on land and shallow offshore locations, the saturation point is 80 terawatts for 1,500 installed terawatts of installed power. "

Storage, storage, storage. The problem with wind isn't that there isn't enough of it, it's that it doesn't blow in the right place at the right time. Here in the southern US we need electricity to run air conditioning on hot summer afternoons when the air is stagnant. How do you get the power from where the wind is blowing to where it's not blowing? Or store it until it's needed?

Hydrogen Fuel? Use the windturbines near the coasts to generate hydrogen fuel which is then pumped/transported to areas that need it.

Alternativly we simply don't rely on one source of power and in your case of hot summer days: solar energy sources.

Ok, so the result of this study is to give up on wind. Really that's what it's saying not only is it physically impractical to harness enough land area (and resorting to the Sea). It most glaring omission is the economic issue - that wind turbines flat out cost too much, and they are a heavy maintenance item.

For distributed power, small 5 to 50-megawatt neighborhood traveling wave reactors are the answer. I say this is plausible because the article invoked a mythical beast - the jet stream windmill. I have never seen one, or the design for one. Meanwhile I've seen the design for 2 traveling wave reactors.

We should all stop with the Don Quixote-esque fantasy of chasing windmills.

Meanwhile back in the read world, Sharp has developed a solar cell with <a href="http://news.xinhuanet.com/english/sci/2012-05/31/c_131623501.htm"> 43% efficiency</a>. This is at or better than the efficiency of wind. Now consider the amount of area you have to devote to a wind mill. Those things are HUGE. Would you rather spend that on a hard-to service, mechanical device or a solid-state zero service device?

Storage, storage, storage. The problem with wind isn't that there isn't enough of it, it's that it doesn't blow in the right place at the right time. Here in the southern US we need electricity to run air conditioning on hot summer afternoons when the air is stagnant. How do you get the power from where the wind is blowing to where it's not blowing? Or store it until it's needed?

The latter has been everything to compressed air, to flywheels, to superconductors.

Or how about we install 4000 Gigawatt nuclear plants instead. Use far less real estate, you can put them anywhere they're needed, and if built properly (IE containment domes and modern safety systems) won't hurt anyone.

Just because wind power is fashionable doesn't make it good engineering!

Leaving out the issue of waste management hasn't currently been adequately dealt with.

"At the much more reasonable power levels of simply meeting global demands, both studies reported minimal environmental impacts. Local temperatures could change around one degree Celsius, while local precipitation could be affected by about 10 percent."

Ummm, given the 300 million turbines required "local" is going to be a lot of places. Given the shrill panic over the less than 1 deg C change in temperature of our current warming trend, I fail to see how this is a "minimal" impact.

I for one worry about the minor 10% change in precipitation. That is a drastic change. Imagine a monsoon with 10% more rain, or what if deserts get 10% less rain than they already receive, how many more creatures would we be killing. Not to mention that I'm sure neither study actually accounted for everything that sucking that much wind power would change. If we actually sucked that much power from the wind, we would lose wave height in the ocean, any number of changes. Also as stated above, lol at the giant zeppelins plugged into the ground with big ass orange extension cords.

Didn't realise there were any climate implications of wind turbines; that's interesting.

Could someone please enlighten me though as to why there's two quoted numbers, like the 250 terwatts vs 3000 terwatts? Tad confused..

" Jacobsen and Archer found that, with turbines placed all over the planet, including the oceans, wind power saturates at about 250 terawatts, corresponding to nearly three thousand terawatts of installed capacity. If turbines are just placed on land and shallow offshore locations, the saturation point is 80 terawatts for 1,500 installed terawatts of installed power. "

Wind turbines are rated in terms of the amount of power they could produce if the wind was blowing at the maximum speed they're able to handle; that's the 1500/3000TW number. But since the wind rarely blows at that level and power extracted is a function of windspeed cubed the average power produced is much lower, that's the 80/250TW number.

Ok, so the result of this study is to give up on wind. Really that's what it's saying not only is it physically impractical to harness enough land area (and resorting to the Sea). It most glaring omission is the economic issue - that wind turbines flat out cost too much, and they are a heavy maintenance item.

For distributed power, small 5 to 50-megawatt neighborhood traveling wave reactors are the answer. I say this is plausible because the article invoked a mythical beast - the jet stream windmill. I have never seen one, or the design for one. Meanwhile I've seen the design for 2 traveling wave reactors.

We should all stop with the Don Quixote-esque fantasy of chasing windmills.

Meanwhile back in the read world, Sharp has developed a solar cell with <a href="http://news.xinhuanet.com/english/sci/2012-05/31/c_131623501.htm"> 43% efficiency</a>. This is at or better than the efficiency of wind. Now consider the amount of area you have to devote to a wind mill. Those things are HUGE. Would you rather spend that on a hard-to service, mechanical device or a solid-state zero service device?

There is no future for wind.

Right, because of course if it doesn't solve 100% of our power needs then there's "no hope" for it.

No device is "0 service". You'll be constantly monitoring and servicing these traveling wave generators because it would be frigging insane not to be, they're filled with a very large amount of extremely dangerous material. That of course brings up the NEXT issue, which is hiring a squad of security people to keep each and every one of them secure, and another security organization to watch that one, etc.

High altitude wind turbine designs DO in fact exist. http://en.wikipedia.org/wiki/Airborne_wind_turbine (10 seconds of google search BTW) shows that they are every bit as real as the equally non-existent traveling wave generator, and almost as real as the currently non-existent molten salt thorium reactors, etc. I submit that the wind power alternative, given that it doesn't rely on managing any sort of dangerous waste, is likely the most palatable and by far the most easily implemented option.

Concerns about consistency of wind power are far overblown. Installations spread across the East Coast of the US would almost never produce less than about 50% of installed power. Nor would the required upgrades to the power grid be absurdly expensive (and are largely needed anyway). This plan is already going forward and known to be workable. When combined with hydro power, some energy storage, and a mix of gas and nuclear providing some added cushion we can viably derive the vast majority of our power from wind. There are also alternatives to the backup, such as dry geothermal, solar, and even larger scale grids (an integrated Western Hemisphere grid would pretty well obviate any chance of running out of wind power on any day whatsoever).

If you'd stop with the blinders and objectively look at all the facts you'd see that sadly your pet nuclear power theories just don't hold up. Its cute and all, but time to live in the real world if you ask me.

That wind power for 100% of the world's energy needs is infeasible does not surprise me much. However, that does not mean that it is not a part of the solution. For example, power transmission losses over long distances can be significant enough that a local wind power station becomes economical for a small rural community. Heck, take a large enough cit (wind and solar are the only ones you'd want inside a city) and the same may well be true, as transmission in cities usually uses lower voltages.

(Note that other types of power plants are typically more efficient the larger they are, due to economies of scale, whereas for wind power the opposite is true.)

"At the much more reasonable power levels of simply meeting global demands, both studies reported minimal environmental impacts. Local temperatures could change around one degree Celsius, while local precipitation could be affected by about 10 percent."

Ummm, given the 300 million turbines required "local" is going to be a lot of places. Given the shrill panic over the less than 1 deg C change in temperature of our current warming trend, I fail to see how this is a "minimal" impact.

I was thinking the same thing, if this was a study on the probable effects of global warming, i really doubt Ars would report a 1 degree change and 10% precipitation effect as 'minimal environmental impacts'

So, "experts" say that harnessing windpower from so many turbines will not affect climate.

Might be true, but that is only when those turbines have been manufactured, transported and installed. Before that comes mining and shipping raw materials from all over world across to China (and may be some other places). Building so many turbines, is going to require how much mining activity across the globe?

What about climate impact of all of above. Probably the researchers realised that they will never be able to compute that - and thought to give it a miss.

My fear is that some stupid climate change evangelist or wind power industry will use this comments from articles like these to push their own agenda. Unbalanced articles and unconsidered impacts like this are dangerous. Even if authors are not serious - someone is going to use the statements and claims made in this article for their own agenda.

I was thinking the same thing, if this was a study on the probable effects of global warming, i really doubt Ars would report a 1 degree change and 10% precipitation effect as 'minimal environmental impacts'

"At the much more reasonable power levels of simply meeting global demands, both studies reported minimal environmental impacts. Local temperatures could change around one degree Celsius, while local precipitation could be affected by about 10 percent."

Ummm, given the 300 million turbines required "local" is going to be a lot of places. Given the shrill panic over the less than 1 deg C change in temperature of our current warming trend, I fail to see how this is a "minimal" impact.

300 million turbines would be to extract 100% of the theoretically feasible power from the atmosphere. That would be roughly 15x current demand, 250 TW vs demand of 18 TW. So, if we look at what we would ACTUALLY need, it would only take 20 million turbines, which means we could probably afford to place them where they have the least significant environmental impact. Presumably the actual impact in this case would be almost immeasurably small. Remember too, nobody is really proposing that we want to or practically could generate 100% of our power from wind. Lets imagine the actual number was 50%, then we're talking about 10 million turbines. This seems like a perfectly feasible number. The US for instance would probably in this case have 2-3 million of them, or maybe 60,000 or so in most states. They would certainly be ubiquitous, but since many would be either offshore or at high altitude probably not as intrusive as you might imagine.

Right, because of course if it doesn't solve 100% of our power needs then there's "no hope" for it.

No device is "0 service". You'll be constantly monitoring and servicing these traveling wave generators because it would be frigging insane not to be, they're filled with a very large amount of extremely dangerous material. That of course brings up the NEXT issue, which is hiring a squad of security people to keep each and every one of them secure, and another security organization to watch that one, etc.

The whole idea of a traveling wave reactor is that it is marginally fissionable. In fact, in the Toshiba design the entire fuel rod is sub-critical. it uses a reflector ring to make it critical. We have all the storage and all the fuel already produced that we'd need for centuries.

There is no reason to hire any security personnel because it is not sufficiently enriched to be desirable. If someone stole it, they power would go out and everyone would notice. These reactors are installed in the ground, so no one can get to them.

Because they are small and minimally critical (the only critical part is where the reflector is) you can't have a run-away reaction. If your reflecto jams, the power goes out. If it travels too fast, it doesn't produce enough energy and that gets noticed too.

There is no extremely dangerous material. We regularly use depleted uranium in shielding for tanks. We only have to enrich it slightly more than what it already is.

I understand that. I also read where the article goes on to say that the lower limit of 300 million turbines is not practical or even really feasible. A quick bit of math would roughly indicate one turbine per square mile of the earths surface with the surface of the earth calculated at ~316,900,000 mi sq. This does not include turbines located 10km up in the jet stream where current engineering restraints meet airplanes somehow. My point is, and Psygard noted as well, this article ultimately comes off in the end as speculation and conjecture at best.

Sure, but that's the point. Knowing the theoretical limits of something is incredibly useful because it gives you a real global upper bound for something. What you're upset about is the fact that this is basic research instead of applied research.

±10% change in expected rainfall is -anything- but insignificant. But I'm assuming the number of installations needed to reach that potential is still in the low millions, at which point other environmental considerations could be more pressing, correct? Wildlife impact is the obvious worry...

"At the much more reasonable power levels of simply meeting global demands, both studies reported minimal environmental impacts. Local temperatures could change around one degree Celsius, while local precipitation could be affected by about 10 percent."

Ummm, given the 300 million turbines required "local" is going to be a lot of places. Given the shrill panic over the less than 1 deg C change in temperature of our current warming trend, I fail to see how this is a "minimal" impact.

I was thinking the same thing, if this was a study on the probable effects of global warming, i really doubt Ars would report a 1 degree change and 10% precipitation effect as 'minimal environmental impacts'

I think what the study is trying to point out here is that is the worse-case scenario IF we wanted to generate ALL our power needs from wind. Since that's never going to be realistic, don't worry about the climate effect from wind generartion since it should be minimal (possibly statistically indestingushable from zero) at the scales we will REALISTICALLY build at.

"Ummm, given the 300 million turbines required "local" is going to be a lot of places.

300 million turbines is the saturation point, not the needed number. 300 million turbines would generate far more power than we need. Look at the caption on the image at the top of the article. 4 million turbines could provide half the power we need.

"Ummm, given the 300 million turbines required "local" is going to be a lot of places.

300 million turbines is the saturation point, not the needed number. 300 million turbines would generate far more power than we need. Look at the caption on the image at the top of the article. 4 million turbines could provide half the power we need.

If one figures around 3.5 to 4 million dollars for a commercial grade wind turbine final cost in ground, that's around 14-16 trillion dollars. Add in substations and related infrastructure to regulate widely varying power outputs and loads on the nations grids (plural, they're not fully meshed correctly nationally our power delivery engineers here tell me) and the total costs outstrip the sum total of our national debt. That might be a hard sell to investors, among other hurdles.

Kyle Niemeyer / Kyle is a science writer for Ars Technica. He is a postdoctoral scholar at Oregon State University and has a Ph.D. in mechanical engineering from Case Western Reserve University. Kyle's research focuses on combustion modeling.